Operation Techniques
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4.6.2 Calculated Neutral Current
For 4-wire connections, the
PM295
provides calculation of the neutral current,
which comprises the current that returns through the neutral conductor along with
the ground leakage. The range of measurement is the same as for phase currents.
The parameter is accessible via the front panel and communications, and can trigger
a setpoint.
In the event of a 3-wire connection, the neutral current is not calculated.
4.6.3 Auxiliary Current Input Operation
The
PM295
has an auxiliary current input option (upon order) that allows an
additional current to be measured with independent user-defined scaling. The
AUXILIARY CT PRIMARY CURRENT
is specified by the user. The auxiliary
current reading is accessible via the front panel and communications, and can be
used as a trigger for setpoint operation.
An auxiliary current input option can be ordered with the secondary rating for the
external CT with a 5 mA, 1 A, or 5A full scale secondaries.
Ground Leakage Measurements
The auxiliary input is typically used for ground leakage measurements with a 5
mA
full scale secondary rating. The current readings will be in mA units.
Direct Neutral Current Measurements
By using the option with the secondary rating of 1 A or 5 A, the auxiliary current
input can be used to measure the current in the neutral or ground conductor. This
will cause the readings to be displayed in Ampere units.
4.6.4 Frequency Measurements
Frequency measurements are the base for all real-time measurements provided by
the
PM295
. Frequency measurements are taken using the phase A and C voltage
inputs. At least one of these inputs must be provided for the frequency to be
measured correctly.
The measurement sensitivity for stable frequency readings is about 30V RMS for
660V input and 8V for 120V input. If the input signal is below the required level,
the frequency will be displayed as zero. In this event, all measurements will be taken
